Flexible metallic tubing



w. E. PHILLIPS 2,832,375

FLEXIBLE METALLIC TUBING Filed May 14, 1954 April 29, 1958 INVENTOR. Wolter E. Phillips Mge/4 ATTORNEY United States Patent FLEXIBLE METALLIC TUBING Walter E. Phillips, Nixon, N. J., assignor to Flexico Products, Metuchen, N. J., a corporation of New Jersey Application May 14, 1954, Serial No. 429,828

1 Claim. (Cl. 138-51) This invention relates to iexible tubing and more particularly to flexible tubing comprised of metal and still more particularly to flexible metal tubing formed from metallic strip material wound spirally upon a mandrel with its abutting edges secured together in an interlocking joint with or without a sealing material disposed in said joint.

The object of the invention is to provide an improved flexible metal tubing. Another object is to provide a relatively light weight exible metal tubing per unit of length having a high crushing strength and high bending properties. Still another object is to provide relatively large diameter flexible metal tubing comprised of relatively thin guaged metal strip, which has a high crushing strength and sutlicient bendability toenable relatively long lengths of the tubing to be coiled up into small diameter coils for shipment. Other objects will be apparent as the invention is more fully hereinafter disclosed.

In accordance with these objects, I have discovered that by providing thin guaged strip material with from one to a plurality of longitudinally extending ribs in the area lying between the edge areas subsequently to be utilized in the forming of the interlocking joint, the crushing strength of the flexible metal tube formed therefrom is increased from a small amount to a large amount depending upon the size, shape and number of said reinforcing ribs. l have further discovered that by locating one of the said ribs in a position disposing said rib in closed spaced relation to the forward edge of the interlocking joint of the tubing and giving to said rib a heighth approximately but slightly greater than the thickness of the said joint the bendability of the said tubing is materially increased as Well as is the strength of said joint and its resistance to deformation under bending stress. l have also discovered that the flexibility of the said tubing is further increased by increasing the heighth of at least one of the other reinforcing ribs provided in said strip as is also the crush resistance of the tubing.

On the basis of these discoveries I am able to design and fabricate a plurality of crush resistant flexible metal tubing from relatively thin guaged metal strip material each designed to meet some specific service use or utility for which prior art flexible metal tubing is either inadequate, too heavy or non-utilizable.

As one specific embodiment of the invention, but not as a limitation thereof, I will disclose and illustrate `the same in the form of a relatively light weight crush resistant iiexible metal tubing having sufficient bending properties permitting relatively long lengths or same to be wound up into small diameter coils suitable for shiprnent. The ilexible metal tubing of this specific embodiment is one that has been designed for particular utility in association with the tensioning units and in the Lee- McCall system of placing concrete structures in a permanent state of compression greater than any tensile stresses would carry under load. In this system of pre-tensioning A concrete structures steel bars or rods specially processed to specilied physical properties are embedded in the concrete structure with the opposite ends thereof enclosed by an engaging nut and plate resting against the exterior surface of the concrete structure holding the bar or rod under tension.

The problem involved in the use of these tensioning bars is to provide in the concrete structure a suitable opening through which the bars may be passed after the concrete structure has hardened. As the length of the bar increases this problem increases and is effectively solved by the specific embodiment of the present invenl10n.

The flexible rnetal'tubing of the instant specific embodiment herein disclosed is designed to solve this problem economically and practically.

Referring to the drawings illustrating the present invention in the specific embodiment- Fig. l illustrates a length of spirallyl wound flexible metal tubing constructed in accordance with the present invention with said length shown partly in broken away section to enable one skilled in the art to recognize the improvement of the present invention;

Fig. 2 is an end view of the same;

Fig. 3 is an enlarged sectional view in perspective taken along plan 3-3 of Fig. 2;

Fig. 4 is a side view of a length of the tubing subjected to two (2) angles of bend;

Fig. 5 is an enlarged cross section indicating the flexible properties of the tubing under tensile stresses;

Fig. 6 is an enlarged cross section indicating the flexible properties of the tubing under compression stresses; and

Fig. 7 is an enlarged sectional View showing a modied form of the invention.

In the drawings, the tubing T (Fig. l) which may have substantially any desired diameter, from relatively small to relatively large diameter, is in this example of a diameter of 13/8 inches (inside) and 11/2 inches (outside) and is comprised of a cold formable metal strip having a guage thickness of .008 inch and a width. of l inch. The strip material of the instant specic embodiment is comprised of soft annealed cold rolled steel.. Alternatively, the said strip may be comprised of substantially any suitable metallic material such as stainless steel, copper and its alloys, aluminum and its alloys, brass, bronze, and many other suitable cold formable metallic strip materials without departure from the present invention.

Referring to the drawings, the tube T is illustrated as a spirally wound product with the abutting edges of strip S bent over and folded together into an interlocking joint l'. This interlocking joint J is, per se, old and well known in the art and, per se, forms no part of the present invention except as one of the necessary and essential elements thereof. Heretofore, however, such interlocking joints have had limited flexibility and have had low resistance to distortion under either compression or tensile stresses.

In accordance with the instant invention, the strength of this joint J and its resistance t0 distortion under tensile and compression `stresses have been greatly increased by providing in the said strip S a longitudinally extending rib R prior to forming the strip into the tube T.

The rib R, as may be noted in Fig. 3, which is a perspective view taken along plane 3-3 of Fig. 2, is substantially V-shaped in cross section with one leg a lying in a plane substantially perpendicular to the surface of the strip S and with the other leg b lying in a plane at an acute angle thereto. The heighth of the rib R is preferably approximately but slightly greater than the thickness of the joint I and the rib R is disposed in the strip S in a position that will locate the rib R in relatively close spaced relation to the forward edge of the joint l.

tube T, the rib R performs another important function.

This additional function is illustrated in 4, 5 and 6, to which reference now should be made. As shown in Fig. 4, when the tube T is bent in an arc which .may vary from a small angle to as much as 90, the rib it incr the resistance of the tube T to mechanical deforma under the compression and tensile stresses applied increases the bending properties of the tube T.

ln Fig. 4 is shown a length of a tube T which is bent in one section about an arc having a radius of 51/2 inches and in another section about an arc having a radius of 11A inches. The angle of bend in the second section is substantially sufficient to provide a 90 bend to the tube T.

ln Figs. 5 and 6 is illustrated in enlarged cross section the effect obtained when the angle of bend of the tube T is substantially 90. In Fig. 5 the effect of tensile stresses along the outer face of the tube T is shown. A comparison of the joint I and rib R yof Figs. 3 and 5, should be made. It will be noted that when the tube T is bent y the part of the tube subjected to tension stress will move substantially as follows:

The interlocking leafs l-l of the joint J will lirst move relative to each other to Close up the space gaps g g provided in the joint I for moderate flexibility in the tube T. As the tensile stress increases beyond that necessary to produce .the result the rib R opens with the leg a moving out of the perpendicular to an angle to the perpendicular. When. the tensile stress is further increased as by increasing the angle of bend, the rib R can open to the point where it is substantially concentric with the joint I. In this position, however, the flexibility `of thc rib R has been substantially destroyed and the tube T thereafter cannot be returned to its original position. i

However, until the elastic limit of the metal has been exceeded under such tensile stresses the tube T usually can be returned to first position.

Referring now to Fig. 6, the effect of compressi-on stresses can be noted. The section of the tube T illustrated is that section diametrically opposite to the section shown in Fig. 5. As may be noted, the first effect of compression stress is to pinch the legs a and b together and to force the leg a downwardly and against the joint l pinching the interlocking leafs /-l of the joint together and securing them in this position against relative movcments. This movement of rib R brings the outer edge of the rib R in a position above and over the joint l further preventing the joint from opening up under cxtreme compression stresses.

As the rib R bears downwardly on and against the joint] the joint l is forced sideways against the fold f of the adjacent section which is pinched together and moved downwardly onto the opposite edge of the joint i to se- This 7 is of great importance where the joint I is desired to remain fluid tight, as in the instant specific embodiment.

Where the joint I is desired to be absolutely fluid tight, the said joint may be formed with a packing material disposed between the interlocking leafs of the joint, as heretofore done in the art, which will generally have the effect of severely limiting the .relative movement of the leafs l-l under tensile stress and throwing the flexibility factor under tensile stress substantially wholly upon the rib R.

Under these conditions it is desirable to provide one or more Vadditional ribs R in the strip S substantially as indicated in Fig. 7.

In the modification shown. in Fig. 7, a second reenforcing and flexing rib R is provided to increase the crush resistance of the tube T and to increase the angle of bend of the tube T, and the flexibility of the tube T under tensile stress. If desired, a plurality of such ribs R may be provided in the strip S without departure from the invention, the single rib R shown in Fig. 5 being shown for purposes of example and not for purpose of limitation. The additional rib R' normally is required where the width of strip S is increased materially or where the diameter of the tube T is increased materially or where the joint J is packed .or sealed to fluidproof the joint, as above disclosed.

The sai-d ribs R may be substantially identical in size, shape and configuration to rib R, as shown, or may be of many other shapes, depending upon the main function in View, all as one skilled in the art will recognize as being without essential departure from the scope of the present invention which contemplates the use of from one to a plurality of such auxiliary ribs R having a size, shape and contiguration substantially that of rib R down to a size, shape or configuration relatively smaller than that of rib R, thereby to obtain varying reinforcing and flexing properties, in the tube T to meet varying service conditions.

Having hereinabove disclosed the present invention generically and specifically and having illustrated and disclosed one specific embodiment of same and a modification thereof, it is believed apparent that the present invention may be widely modified without essential departure therefrom and all such modifications and depar tures therefrom are contemplated as may fall within the scope of the following claim.

I claim:

A flexible helically wound metallic tube formed from an elongate strip of exible metallic material, said strip having opposite margina-l edge portions thereof folded back upon adjacent portions of the strip in opposite directions and the juncture of the folds defining outer side edges and with substantially identical folded marginal portions of the adjacent wound portion of the strip disposed between and engaged by said folded portions and with the free ends of the interengaged portions being spaced from the inner junctures of the folds whereby to provide a readily slidable interengaged joint, at least one expansible and contractable and deformable helical outwardly extending rib disposed between the inner and outer folds at the opposite ends of the strip, a portion of the rib being disposed opposite to and in alignment with the adjacent fold and in spaced relation therewith, the width of the space between the fold and the portion of the rib being greater than the said spacing of the free ends of the folds from the juncture of the folds, whereby the tube may be expanded due to the slidable joint while maintaining the engagement of that joint and further the tube may be contracted so that the fold engages the adjacent portion of the rib to limit the contraction and prevent disengagement of the slidable joint, and when the tube is bent the rib will be compressed on the inner side of the bend and will be gradually and increasingly enpandedfrom the inner side to a point of maximum eX- pansion substantially diametrically disposed on the outer 1,021,567

side of the bend. 2,118,584

References Cited in the le of this patent UNITED STATES PATENTS 5 35,672

500,847 Bowley July 4, 1893 624,603

507,877 Bowley Oct. 31, 1893 649,079

6 Berryman et al Mar. 26. 1912 Aime May 24, 1938 FOREIGN PATENTS France Oct. 1,1929 Germany Sept. 2, 1936 Germany Aug. 14, 1937 

